1. Field of the Invention
The present invention relates to a method of forming a fine pattern which should be applied to an electronics device such as semiconductor device and liquid crystal device, and relates to a device produced by this method.
2. Description of the Prior Art
FIG. 7 is a process flowchart illustrating a conventional method of forming a fine pattern. In FIG. 7, reference numeral 100 designates a substrate; and 300 designates a work film to be processed; 301 designates a process pattern; 600 designates a resist; and 601 designates a resist pattern.
The operation will be next described below.
The work film 300 such as a conductive film is formed on the substrate 100 (ST1001), the resist 600 is formed thereon by spin coating (ST1002), which is subjected to photolithography so as to obtain the resist pattern 601 (ST1003). Subsequently, the work film 300 is etched through the resist pattern 601 as a mask, thus having the process pattern 301 (ST1004), and finally the resist pattern 601 is removed by way of resist ashing, stripping, and so on, thus completing the formation of a desired fine pattern (ST1005).
FIG. 8 is a process flow chart illustrating another conventional method of forming a fine pattern. In FIG. 8, reference numeral 400 designates an etching mask film; 401 designates a processed etching mask film; and 401a designates a modified etching mask film, which serves as a hard mask to the work film 300. Note that the same reference numerals above denote the same components or corresponding parts and these explanations will be omitted.
The operation will be next described below.
The work film 300 such as a conductive film is formed on the (ST2001), the etching mask 400 is formed thereon, which has an etching rate different from the work film 300 and has a desired selectivity to it. The resist 600 is formed by spin coating (ST2002), which is subjected to photolithography, thus having the resist pattern 601 (ST2003). Subsequently, the etching mask film 400 is etched till the surface of the work film 300 of a negative pattern section is completely exposed through the resist pattern 601 as a mask, thus bringing the processed etching mask film 401 (ST2004).
After the resist pattern 601 is removed by way of resist ashing, stripping, and the like, a film of which the etch rate is different from the work film 300 to serve as a mask to the work film 300 during etching is subjected to an isotropic etching process unselectively, thus having the modified etching mask film 401a (ST2005), and then when the work film 300 is etched through the film 401a as a hard mask, the formation of a desired fine pattern is completed (ST2006).
The conventional methods of forming a fine pattern are configured as described above. In summary, one method is as follows: as shown in FIG. 7, the resist pattern 601 is formed on the work film 300, and etching is performed through the pattern 601 as a mask, thus forming the process pattern 301. Alternatively, another method is as follows: the work film 300 is etched through a film of which the etching rate is different from the work film 300 to serve as a mask to it during etching, thus forming the process pattern 301. However, the process pattern 301 formed by these methods has a problem that a pattern formation beyond resolution by lithography technology is impossible.
Alternatively, as shown in FIG. 8, it is considered that with respect to the film of which the etch rate is different from the work film 300 to serve as a mask to it during etching, isotropic etching is unselectively performed for pattern processing, and the work film 300 is etched through the resultant pattern as a hard mask, having the process pattern 301. However, in this case, all the parts of the remaining patterns are shrunk, which may lead to difficulties on pattern designs.
The present invention is implemented to solve the foregoing drawbacks. It is therefor an object of the present invention to provide a method of forming a fine pattern that only line or left patterns to be required may be shrunk, resulting in a desired pattern on the designs, and a device manufactured by the above method.
According to a first aspect of the present invention, there is provided a method of forming a fine pattern comprising the steps of: forming a work film to be processed on a substrate; forming a hard mask film which has a different etching rate from the work film and can serve as a mask to the work film; forming a first resist pattern on the hard mask film by lithography; forming a hard mask pattern by etching a first section which is not covered with the first resist pattern till the upper surface of the work film is exposed; removing the first resist pattern; forming a second resist pattern on the hard mask pattern by lithography; etching a second section which is not covered with the second resist pattern by isotropic etching; removing the second resist pattern; and etching the work film through the hard mask pattern as a mask, partially subjected to the isotropic etching.
Here, the work film may be composed of a conductive film, while the hard mask film may be composed of a insulating film.
In addition, the conductive film may be composed of at least one type of polysilicon, tungsten silicide, aluminum, and tungsten, or a multi-layered film thereof, while the insulating film may be composed of either silicon oxide or silicon nitride, or a two-layered film thereof.
Alternatively, the work film may be composed of an insulating film, while the hard mask film is composed of a conductive film.
Further, the insulating film may be composed of either silicon oxide or silicon nitride, or a two-layered film thereof, while the conductive film may be composed of at least one type of polysilicon, tungsten silicide, aluminum, and tungsten, or a multi-layered film thereof.
In this case, the isotropic etching may be performed by wet etching.
Furthermore the aforementioned method may comprise a step of forming an antireflection film before the step of forming the first resist pattern.
According to a second aspect of the present invention, there is provided a method of manufacturing semiconductor device or liquid crystal device employing a method of forming a fine pattern comprising the steps of: forming a work film to be processed on a substrate; forming a hard mask film which has a different etching rate from the work film and served as a mask to the work film during etching; forming a first resist pattern on the hard mask film by lithography; forming a hard mask pattern by etching a first section which is not covered with the first resist pattern till the upper surface of the work film is exposed; removing the first resist pattern; forming a second resist pattern on the hard mask pattern by lithography; etching a second section which is not covered with the second resist pattern by isotropic etching; removing the second resist pattern; and etching the work film through the hard mask pattern partially subjected to the isotropic etching and serving as a mask.